Burglar alarm



1953 w. H. OBROCK 2,649,751

BURGLAR ALARM Filed Jan. 26, 1950 2 Sheets-Sheet 1 Waller hf. Obrock INVENTOR.

Aug. 25, 1953 w. H. OBROCK 2,649,751

BURGLAR ALARM Filed Jan. 26. 1950 2 Sheets-Sheet 2 if M 66 Fig. 5. Walter H- Obrock INVENTOR.

Patented Aug. 25, 1953 UNITED STATES PATENT OFFICE BURGLAIt ALARM Walter H. Obrock, St. Louis, Mo.

Application January 26, 1950, Serial No. 140,602

3 Claims.

This invention relates to signalling devices and more particularly to a spring actuated burglar alarm.

An object of this invention is to provide a burglar alarm of comparatively small size which may be readily mounted on a door or the like which is readily actuated by an unauthorized opening of the door.

A further object of the invention is to provide a spring actuated burglar alarm eliminating the necessity for electricity or other means of power.

Yet another object of the invention resides in the provision of a burglar alarm having locking means associated therewith While inactivating the alarm.

Still further objects of the invention reside in the provision of a burglar alarm that is strong, durable, highly efficient in operation, simple in construction and design, capable of being readily used and cheaply manufactured, and quite unobtrusive in appearance.

These, together with the various ancillary objects of the invention which will become apparent as the following description proceeds, are attained by this burglar alarm, a preferred embodiment of which has been illustrated in the accompanying drawings, by way of example only, wherein:

Figure 1 is a rear elevational view of the burglar alarm comprising the present invention with parts thereof being broken away to show other parts in greater detail;

Figure 2 is a top plan view of the invention with the casing being broken away and shown in section to show the coacting elements of the invention;

Figure 3 is a front elevational view of the invention shown in operative installation on a door;

Figure 4 is a vertical sectional view as taken along line 4--4 of Figure 2;

Figure 5 is another vertical elevational view as taken along line 5-5 of Figure 2; and

Figure 6 is a sectional detail of the trigger actuated mechanism for permitting actuation of the burglar alarm.

Figure 7 is an elevational view of the alarm sounding member comprising one element of the invention.

With continuing reference to the accompanying drawings wherein like reference numerals designate similar parts throughout the various views, reference numeral It! generally designates the burglar alarm comprising the present invention. As can be readily seen, the burglar alarm [0 includes a casing l2 which has attached thereto by suitable screws M or the like, U-shaped brackets l6 which are used for securing the casing l2 to the inner panel of a door 18 or like access opening using screws 20 or other suitable means. The casing cover plate 22 is secured to the rest of the casing by screws 24 after the device has been secured to the door l8.

Rotatably mounted in the casing l2 and operatively connected to a spring motor 28, is a drive shaft 25 that fixedly supports a drive gear 32 and which rotatably supports fixedly connected ears 26 and 34. A supporting shaft fixed in casing I2 parallel to drive shaft 25 rotatably supports fixedly connected gears 30 and 38 that mesh with gears 26 and 32, respectively. An additional shaft 32 is fixed in casing l2 and rotatably supports a driven gear 38 that meshes with the gear 34 and which fixedly supports a lug 40 for engagement with a sounding member 42 having a shaft 44 made of resilient metal for intermittent contact with gong 46 in casing l2.

As the shaft 25 is driven by a spring motor 28, gear 32 will rotate to drive gears 36 and 30, and as gear 30 is meshed with gear 26, gears 28 and 34 Will rotate and gear 34 will drive gear 38.

The control gear 30 is formed with a slot or aperture 48 therein and additionally has a lug 50 welded or otherwise attached thereto. A worm gear lock 54 actuated by a key and having a locking pin or plunger 56 actuated thereby is installed in the door I8. When it is desired to prevent the alarm from being actuated it is merely necessary to rotate the worm gear lock 54 to drive the lock pin 56 into the slot or opening 48 by means of positioning the control gear 30 through use of the key, companion gear 32 and gear 36 to properly position the control gear 30.

As shown best in Figure 6, secured to the upper wall of the casing I2 is a tubular member 58 which has a cylindrical rod 60 slidably mounted thereon. The cylindrical rod is in engagement with the lug 58 when the alarm is in its set position and is held there by spring stop member 62 which is rigidly secured to the door frame 64. Obviously when the door is opened the rod 60 which is formed with a semi-hemispherical cap 68 thereon is disengaged from the spring stop 62 so that the rod 68 may be lifted out of engagement with the lug 50 due to the action of the spring 28 whereby the gong 46 may be actuated by rotation of the shaft which in turn actuates gear 38 to sound the gong member 46 through sounding member 42. As desired, to more readily transmit the sound, a plurality of louvres 68 may be formed in the casing walls of the burglar alarm.

Since from the foregoing the construction and advantages of this burglar alarm are readily apparent, further description is believed to be unnecessary.

However, numerous modifications will readily occur to those skilled in the art after a consideration of the foregoing specification and accompanying drawings, it is not intended to limit the invention to the precise embodiment shown and described, but all suitable modifications and equivalents may be resorted to which fall within the scope of the appended claims.

I-Iaving described the invention, what is claimed as new is:

1. In a burglar alarm, an alarm mechanism comprising a drive shaft, a drive gear fixedly connected to said drive shaft, a control gear operatively engaging said drive gear, key operated locking means selectively engaging said control gear for locking said drive shaft against rotation, and trigger means selectively engaging said control gear preventing rotation of said drive shaft, said control gear having an aperture therethrough disposed radially inwardly from the toothed edge of said control gear, said locking means selectively engaging said control means in said aperture.

2. A burglar alarm comprising a casing adapted to be mounted on a door and engageable with a stop member mounted on a door frame, a drive shaft in said casing, means for actuating said. drive shaft, a control gear operatively connected to said drive shaft, said control gear having an aperture therethrough, a lock in said door, a locking plunger selectively engageable with said con trol gear upon actuation of said lock for locking said control gear and said drive shaft against rotation, said lock including a worm gear for advancing said locking plunger, said locking plunger being engageable with said control gear within the aperture therein, means engageable with said stop member selectively preventing rotation of said drive shaft and said control gear, and a sounding member operatively connected to said drive shaft actuated upon rotation of said drive shaft.

3. A burglar alarm comprising a casing adapted to be mounted on a door, a spring driven shaft in the casing, a control gear operatively connecte to the shaft and disposed in the casing, a signal device housed in the casing and actuated upon rotation of said shaft, said control gear having an aperture therein and a radially projecting lug on one face, a spring urged plunger slidably carried by the casing for engaging the lug to prevent rotation of said control gear when the plunger is retracted upon engaging a stop member mounted on a door frame, a locking plunger slidably carried by said casing and movable into and out of said aperture in said control gear, and a key operated door lock operatively connected to said locking plunger for selectively moving the locking plunger into and out of the aperture in said control gear, said aperture being in registry with said locking plunger to receive the latter when the spring-urged plunger is depressed to engage said lug.

WALTER H. OBROCK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 732,727 Fletcher July 7, 1903 1,109,329 Farrell Sept. 1, 191% 2,469,528 Suma May 10, 1949 

